Alkylation process



Fb. 1s, 195s H, M. KNIGHf ET AL 2,824,161

ALKYLATION PROCESS Filed June 13, 1956 United States Patent O ALKYLATION PROCESS Harmon M. Knight, La Marque, and Joe T. Kelly, Dickinson, Tex., assignors to The American Oil Company, Texas City, Tex., a corporation of Texas Application June 13, 1956, Serial No. 591,225

12 Claims. (Cl. 260-683.44)

This invention relates to the reaction of isoparafiins or aromatic hydrocarbons and olefins. More particularly it relates to the alkylation of isobutane with ethylene.

ln the petroleum industry today, the octane race has placed a strain on facilities and materials needed to make gasoline meeting present day automotive engine requirements. One of the remaining sources of high octane components is the product of the alkylation of isobutane and ethylene. This alkylation is not easy to carry out, particularly on a large scale.

An object of the invention is the alkylation of isoparafiins, particularly isobutane, with olefins, particularly ethylene. Another object is the alkylation of aromatic hydrocarbons with olefins. Other objects will become apparent in the course of the detailed description.

The alkylation of isoparafiins or aromatic hydrocarbons with olefins is carried out in the presence of a novel catalyst pair. One member of the catalyst pair is boron trifluoride. The other member of the catalyst pair is a hydrate of borotungstic acid, cadmium borotungstate, or nickel borotungstate. Although the second component of the catalyst pair is spoken of as a promoter hydrate, it is believed that the solid member is more properly a complex of the defined acid or borotungstate hydrate and EP3; the BP3 is believed to complex with some or all of the hydrate water present in the defined acid or borotungstate salt. More than the amount of EP3 needed to complex the water of hydration is necessary to obtain the desired catalytic effect.

Boron trifluoride is one member of the catalyst pair. Commercial grade anhydrous boron triuoride is suitable for use as one member of the catalyst pair.

The other member of the catalyst pair, hereinafter spoken of as the promoter, contains water of hydration. The promoter may be used as a fine powder, as pellets, or may be supported on a solid carrier such as alumina, charcoal, silica gel, etc. Not all borotungstates which contain water of hydration are suitable, nor are all metal ions suitable. The effective promoters are borotungstic acid, cadmium borotungstate and nickel borotungstate. The solid borotungstic acid may not contain water of hydration in the strict sense but some combined water must be present. In determining the effective members, it has been considered that the catalyst pairs which did not produce a yield, on a weight percent basis on ethylen e charged, when isobutane and ethylene were contacted, of 100% or more, were unsuitable.

The anhydrous solids do not have any promotional effect on the activity of EP3. In those cases wherein various amounts of water of hydration may be present, it is not necessary that any particular amount be present.

The BP3 and the definedsolid react to form a solid material containing complexed EP3. When the solid member and EP3 are contactedin a closed vessel, the EP3 partial pressure drops very rapidly at first and then gradually approaches a constant value. It appears that a very rapid ice reaction between the BP3 and some of the water of hydration takes place. This initially rapid reaction is then followed by a relatively slow reaction between the remaining molecules of hydrate water and additional BF3. It appears that when the hydrate is exposed to EP3, even in the presence of hydrocarbon reactants, eventually all of the water of hydration will become associated with BP3 on about a 1 mole of BP3 per mole of hydrate water basis.

A complex of the defined hydrate and BP3 is not an effective catalyst for the alkylation in the absence of free- BF3. Prec-EP3 is to be understood as EP3 existing in the reaction zone which is not complexed with the defined hydrate. As soon as the hydrate has complexed with some EP3, the beneficial catalytic effect exists. Thus free-EP3 may exist in the reaction zone, as evidenced by the formation of alkylate, even though all of the hydrate water has not been complexed. lfn a batch system, wherein less BP3 is present than is theoretically required to complex all the water of hydration present in the hydrate, eventually no alkylation will occur as charge is added, since all of the BP3 will become complexed.

In general, the process is carried out utilizing an amount of BP3 which is in excess of that required to complex with all the hydrate water present in the contacting zone, namely, ,in excess of about l mole of BP3 per mole of hydrate water present. More than the minimum amount of free-EP3 is beneficial, in fact, the yield of alkylate increases rapidly with increase in free-BP3 present, up to a maximum amount. The amount of free-EP3 used is dependent somewhat upon the reactants themselves. However, when reacting isoparafiins and olefins, the free- BP3 usage is desirably, set out on a BP3 to olefin weight ratio, of at least about 0.2. In other words, at least about 0.2 lb. of free-EP3 per lb. of olefin charged to the alkylation zone is desirable. About 1.5 parts by weight of EP3 per part of olefin charged appears to be about the desirable maximum usage of BP3. It is preferred to use between about 0.35 and l part by weight of free-EP3 per part by weight of olefin when utilizing the lower molecular weight olefin, such as ethylene and propylene.

The process may be carried out at any temperature below the temperature at which the defined hydrate decomposes, that is, loss of all its Water of hydration. The temperatures of operation may be as low as -20 C. or even lower. Temperatures as high as 150 C. and even higher may be used with some of the hydrates which have relatively high decomposition temperatures. More usually the temperature of operation will be between about 0 C. and 100 C. Lower temperatures appear to favor the formation of the hydrocarbons having 6 to 7 carbon atoms. It is preferred to operate at a temperature between about 25 C. and 40 C.

Sufficient pressure is maintained on the system t o keep a substantial portion of the hydrocarbons charged in the liquid state. The process may be carried out at relatively low pressures, for example, p. s. i., or it may be carried out at elevated pressures, for example, A2000 p. s. i., or more. In general, pressures Will be between about 200 and 1000 p. s. i. and preferably between about 300 and 600 p. s. i. i

The contacting of the isoparaliin or aromatic hydrocarbon and the olefin in the presence of the defined catalyst pair is continued until an appreciable amount of alkylate has been formed. In batch reactions, ,it is possible to virtually extinguish the olefin, i. e., convert essentially 100% of the olefin by a sufficiently long period of contacting. When operating in a continuous flow system, it may be desirable to have a time of contacting such that substantial amounts of olefin are not con- Patented Feb. 18, 1958 verted and obtain the complete conversion of the olefin by a recycle operation. The time of reaction will be determined by the type of hydrocarbons charged, the ratio of isoparaffin or aromatic to olefin, the degree of mixing inthe contacting zone and the catalyst usage. A few tests will enable one to determine the optimum time of contacting for the particular system of operating conditions being tried.

The reactants in the hydrocarbon charge to the alkylation process are isoparafiin, or aromatic and olefin. The olefin contains from 2 to about l2 carbon atoms. Examples of suitable olefins are ethylene, propylene, butene- 2, hexene and octene; in addition to these, the olefin polymers'obtained from propylene and/or butylene are also suitable for use in the process, such as codimer, propylene trimer, propylene tetramer and butylene trimer. It Vis preferred to operate with ethylene or propylcne.

' The aromatic hydrocarbons must be alkylatable by the particular olefin used. It is self-evident that an aromatic hydrocarbon which contains alkyl substituents positioned so that steric hinderance would prevent or greatly reduce the possibility of alkylation with the particular olefin should not be subjected to the process. Examples of particularly suitable aromatic hydrocarbons are benzene, toluene, xylene, trimethylbenzenes, and the other alkyl analogues, such as propyl and butyl; the naphthalene aromatic hydrocarbons, such as the mono and di-substituted methyln'aphthalenes.

The isoparafn reactant is defined as a parafiinic hydrocarbon which has a tertiary hydrogen atom, i. e., paraflins which have a hydrogen atom attached to a tertiary carbon atom. Examples of these are isobutane, isopentane (Z-methylbutane), Z-methylpentane, 2-methylhexane, 3-methylhexane, 2,3-dimethylbutane (di-isopropyl) and 2,4-dimethylhexane. Thus the isoparaflins usable as one reactant in the process contain from 4 to 8 carbon atoms.

. VIn the isoparafiin-olen system, the alkylation reaction is more favored as the mole ratio of isoparain to olefin increases. In general, the isoparaiiin to olefin mole ratio in the hydrocarbon charge should be at least 1. More than this amount is good and it is desirable to have an isoparafin to olefin ratio between about 2 and 25 and in some cases more, for example, as much as 50. It is preferred to operate with an isoparaiiin to olefin mole ratio of between about 5 and 15.

The presence of non-reactive hydrocarbons in the hydrocarbon charge is not detrimental unless the reactants become excessively diluted. For example, the isoparain may also contain isomers of the normal configuration. The olefins may contain paraffins of the same carbon number. Mixtures of 2 or more isoparaiiins or 2 or more aromatic hydrocarbons, or 2 or more olefins may be charged. In general, when a particular product distribution is desired, it is preferable to operate with a single isoparafiin and a single olefin, for example, technical grade isobutane and ethylene, both of about 95% purity. n

The reactants may be mixed together before they are charged into the reactor. Or, they may be charged into the reactor separately. Or, a portion of the olefin may be blended with the isoparaiiin or aromatic before introduction into the reactor and the remainder of the olefin injected into the reactor. The charge may be introduced all at one point into the reactor or it may be introduced at 2 or more points.l The alkylation reaction is somewhat exothermic and temperature control is-facilitated byintroducing the olefin into the reactor at more than one point.

The BF3 member of the catalyst pair may be prernixed with the isoparafin and olefin before introducing these into the reactor but this should not be done when an extremely reactive system such as isobutanes and isobutylene or aromatic hydrocarbons and oleiins are being molecular weight materials.

used; or when an olefin that is very rapidly polymerizable is being used. The BF3 may be blended with the isoparaffin reactant and introduced into the reactor with this member when the isoparain and the olefns are being introduced separately. The BF3 may also be introduced directly into the reaction zone independently from the hydrocarbons charged. The BF3 may be introduced into the reactor at a single point or at several points to help control temperature and reaction rate.

The reactor may be a vessel providing for a batch-type reaction, i. e., one wherein the desired amount of isoparaiiin or aromatic and olefin are charged to a closed vessel containing the catalyst pair and the vessel then maintained at the desired temperature for the desired time. At the end of this time, the hydrocarbon product mixture and unreacted materials are withdrawn from the vessel and processed to separate the alkylate product from the unreacted materials and lower and higher The reactor may be a fixed bed type wherein the reactants and free-EP3 are flowed through the bed of the hydrate member of the catalyst pair, the space velocity being controlled so that the desired amount of reaction is obtained during the passage of the reactants through the bed of hydrate member. Under some conditions, a moving bed of hydrate may be utilized. In still another set of circumstances, a fiuidized bed of hydrate may be utilized with the incoming stream of reactants providing the energy for the fiuidization of the solid hydrate. Other methods of operation common` in the catalytic refining aspects of the petroleum industry utilizing solid catalyst may be readily devised.

It has been pointed out that the solid member of the catalyst pair is really a complex of the solid member hydrate and BF3; the BFS apparently reacting with the water of hydration. The complex may be preformed, by exposing the hydrate to BF3 for a time suiiicient to introduce some BFS into the solid component or even enough to complex all of the water of hydration; this being done before the reactants are introduced into the reaction zone or even before the solid member of the catalyst pair is positioned in the reaction zone. The complex may be formed in situ during a batch-type reaction. In the batchtype operation, it is convenient to introduce all the B133 into the reaction vessel at once. This amount of BFS is sucient not only to complex with the water of hydration but also provide the desired amount of free-B133. In a flow system, the solid member may be prepared in situ by charging fresh hydrate to the reaction zone and forming the complex during the initial passage of reactants and BF3 over the hydrate. Some alkylation reaction occurs even though the hydrate has not taken up sufficient BF3 to complex all the water of hydration. As the flow of reactants and BF3 continues over the solid member, eventually the hydrate will become saturated with respect t0 BF3. At this time, the amount of BFS introduced into the reaction zone should be cut back to that amount of free-BF3 desired, under this particular set of operating conditions.

The illustrative embodiment set out in the annexed figure forms a part of this specification. It is pointed out that this embodiment is schematic in nature, that many items of process equipment have been omitted, since these may be readily added by those skilled in this art and that this embodiment is only one of many which may be devised, and that the invention is not to be limited to thls particular embodiment.

In this embodiment, it is desired to produce a high yield of di-isopropyl for use as a blending material for gasoline. Ethylene from source 11 is passed by way of line 12 into mixer 13. Liquid isobutane from source 14 is passed by way of lines 16 and 17 into mixer 13. Both the ethylene and the isobutane are about purity, the remainder being n-butane and ethane, with trace amounts of other components found in materials derived frorn petroleum rening sources. Mixer 13, in this instance, 1s a simple orifice-type mixer suitable for intermingling a liquid and a gas, or two liquids. Recycle isobutane from line 18 is passed by way of line 17 into mixer 13. In this embodiment, the molar ratio of isobutane' to ethylene is 6,.

From mixer 13, the blend of isobutane andethylene is passed by way of line 19, through heat exchanger 21, where the temperature of the blend is adjusted to 30 C. The temperature of the blend `leaving exchanger 21 is somewhat lower than the reaction temperature, since there is a heat rise in the reactor due to exothermic reaction. From exchanger 21, the stream ot isobutane and ethylene is passed by way of lines 22 and 23 into the top of reactor 24.

Boron triuoride is passed from source 26 by way of valved line 27 and line 28 into line 23, where it meets the stream of isobutane and ethylene. It desirable, a mixer may be introduced into line 23 to insure complete intermingling of the BF3 and the hydrocarbon charged. Recycle BFa is introduced from line 29 by way of lines 28 and 23. In this embodiment, the salt hydrate is completely complexed with respect to BF3 and only the necessary free-B133 is introduced by way of line 28. The weight ratio of free-BF3 from line 28 to ethylene present in line 23 is 1.1.

Reactor 24 is shown as a shell and tube type vessel. The hydrate is contained in the tubes 3 1. The alumina balls 32 and 33 are positioned above and below 'the headers in the reactor to maintain the hydrate within the tubes. In order to maintain the temperature in the reactor at substantially 35 C., Water is introduced into the shell side by way of line 36 and is withdrawn by way of line 37.

In this embodiment, the reactor was charged with borotungstic acid containing about l molecule of water per molecule of acid. The hydrate was preformed into pel.- lets about one-eighth inch in diameter and about oneeighth inch in height. Some silica was present to act as a lubricant in the extrusion of the pellets. The hydrate was contacted with BF3 in an amount such that all of the water of hydration was complexed with BF3. This operation was carried out before reactants were introduced into the reactor. The reactor pressure was maintained at 600 p. s, i. This permits maintaining the isobutane and substantially all of the ethylene in the liquid state.

The product hydrocarbon mixture is passed out of reactor 24 by way of line 41. This stream contains the alkylate product, unreacted isobutane, a small amount of unreacted ethylene and pentanes as well as BF3. The stream from line 41 `iS passed into gas separator 42 where the BF3, isobutane, some pentanes and some alkylate product are taken overhead by way of line 43. The material taken overhead from the separator 42 is passed into fractionator 44.

Fractionator 44 is adapted to separate the BF3 as a gas, the isobutane as a liquid and the higher boilingmaterials as a bottoms product. Fractionator 44 is provided with an internal reboiler 46 and an internal condensor 47. BF3 and unreacted ethylene are taken overhead from fractionator 44 by way of line 48 and may be passed out of the Asystem by way of valved line 49. The material from line 49 may be periodically passed to a BFS purification operation to remove noncondensable inert gases which build up in the system. Ordinarily the stream from line 48 is recycled by way of valved lines 29 and lines 28 and 23 to reactor 24.

Isobutane is withdrawn as a liquid stream by Way of line 51 and is recycled by way of lines 18 and 17 to mixer 13 for reuse in the process. Bottoms product from fractionator 44 is withdrawn by way of line 52 and may be passed to storage or further processing by way of valved line 53. This stream from line 52 consists substantially of isopentane. Some unsaturated C hydrocarbons are also present and also a small amount of higher boiling alkylate material.

The liquids separated in gas separator 42 are passed by way of line 5,6, into fractionator 57. The bottoms product from fractionator 44 may be passed by way of valved line 58 and line 56 into fractionator 57 for complete re,- moval of the alkylate material. In this embodiment, the bottoms are passed to fractionator 57.

Fractionator 57 is provided with an internal reboiler 58,.

and is adapted to produce the desired alkylate products from the hydrocarbon product mixture entering from line 56. A vapor stream is taken overhead by way of line 61, is condensed in cooler 62 and is passed to storage by way of line 63. The material from line 63 consists substantially of isopentane and some unsaturated C5 material. This material may be used as a high octane blending stock for the production of motor gasoline of the desired volatility characteristics.

The alkylate product herein is considered to be that boiling above the pentane range -and boiling below the maximum temperature usable in motor gasoline. In general, a 415 F. endpoint alkylate is blendable into motor gasoline without adverse effect in a speciiication calling for a 400 F. gasoline endpoint. Thus the alkylate product is considered to be the material boiling between about the lower limit of the hexane range and 415 F. in the ASTM distillation procedure.

A considerable difference exists between the octane number of the C6 fraction of the `alkylate product and the higher boiling material. The C6 fraction, which boils from about 110 to 170 F., has an F-l octane number of 101. The C74- material has an octane number which ranges between about 75 and 85, depending somewhat on the fractionation. d

Light alkylate, which includes all the C6 material and some of the C7 material, is withdrawn from fractionator 57 by way of line 66. Heavy alkylate, which includes most of the C7 and materialboiling up to 415 F, is withdrawn from fractionator 57 by way of line 67. A small amount of higher boiling bottoms is withdrawn by way of line 68.

In general, the C6 fraction of the alkylate product will contain from abou-t 86 to about 90 mole percent of die isopropyl (2,3-dimethylbutane). Z-methylpentane and 3-methylpentane represent substantially the remainder of the C6 product. Generally, only trace amounts of n-hexane are present.

The results obtainable by the process of the instant invention are set out in Table I. In these runs, the tests were carried out under what are more or less standard conditions, namely a 4-liter carbon steel bom-b was dried overnight in a stream of hot air at 110 C. The material to be tested (90 grams) was charged to the bomb as a powder and the bomb was evacuated. One kilogram of a dry blend of ethylene and isobutane was added and then BF3 (90 grams) was pressured in. The charged bombs were placed in a rocker and allowed to rock for 20 hours. At the end of this time a liquid sample was drawn through a bomb containing activated alumina (to remove dissolved BF3 and solid particles). This sample Was submitted for Podbielniak distillation. A C6 cut from the Podbielniak distillation was analyzed by mass spectrometer. In some cases `after sampling,V the remaining major portion of the product was debutanized on an Oldershaw column and then fractionated on a packed column.

In Table I, run No. l, the operation was carried out as described above except that no promoter was present in the bomb. The results show that only 34% of depentanized alkylate product was obtained by the use of EP3 alone as the catalyst.

Runs 2, 3, and 4 show borotungstic acid, cadmium borotungstate and nickel borotungstate are eiective promoters. Phosphotungstic acid and silicotungstic acid are ineffective. All these solids contained water of hydration.

TABLE I n.; j

am;Neg@. L. 1 2 a 4--- t 5 f e x'- l Y .Boro- Cadmium Nickel Phospho- Silico- Hydrate None tungstie Borotung- Borotungtungstic tungstic v Acid state state .Acid Aci Conditions:

Isobutane Ethylene (Molar) 3. 2.1 2.9 2.9 2. 6 2. 6 Hydrocar on/Hydrate (Weight) 11. 4 11.1 11.4 11.5 11. 5 BFa/Ethylene (Weight) 0. 7 0.6 0. 8 0. 9 0. 6 0.9 Time, Hours 20 20 20 20 20 Temperature, C 25-35 25-30 25-30 25-30 20-25 25-30 R llilxissuife (Range), p. s. i. g 300 315-230 290-210 285-265 B-258 320-240 es s:

Alkyiate (Depentanized)l (wt. percent)- Pentanes 0 20 17 23 0 13 Hexanes. 21 2 46 56 89 35 19 01+- 13 66 'I 47 15 16 71 Total 34 112 10s 104 51 9o Ethylene Converted, percent 84 74 88 70 2 91% 2,3dimethyibutane.

Thus having described the invention what is claimed is:

l. An alkylation process comprising contacting (a) an alkylatable feed hydrocarbon from the class consisting of (l) isoparaiiin having from 4 to 8 carbon atoms and (2) aromatic hydrocarbon and (b) an olefin having from 21o 12 carbon atoms, in the presence of a catalyst comprising essentially (i) a promoter containing water of hydration selected from the class consisting of borotungstic acid, cadmium borotungstate and nickel borotungstate, and (ii) BF3, said EP3 being present in an amount in excess of about 1 mole per mole of water of hydration in said promoter, at a temperature between about 30 C. and a temperature substantially below the temperature at which said promoter decomposes, and at a pressure suiiicient to maintain a substantial portion of said reactants in the liquid state, and separating a hydrocarbon product mixture containing alkylate product of said feed hydrocarbon and said olein.

. 2. An alkylation process wherein an isoparamn having from 4 to 8 carbon atoms and an oieiin having from 2 to 12 carbon atoms are contacted, in a molar ratio of isopararfin to olefin between about 2 and 50, at a temperature between about C. and 150 C. and a pressure between about 100 and 2000 p. s. i., said pressure being at least suiicient to keep a substantial portion of said reactants in the liquid state, for a time sufiicient to permit an appreciable amount of alkylation reaction to take place, in the presence of a catalyst comprising essentially (i) a promoter containing water of hydration selected from the class consisting of borotungstic acid, cadmium borotungstate and nickel borotungstate, and (ii) boron triuoride, said EP3 being present in an amount in excess of one mole per mole of hydrate water present in said promoter, removing a product hydrocarbon mixture from said contacting zone and an alkylate hydrocarbon product is separated from said mixture.

3. The process of claim 2 wherein said isoparafiin is isobutane.

4. The process of claim 2 wherein said isoparain is 'di-isopropyl;

5. The process of claim 2 wherein said olefin is ethyl ene.

6. The process of claim 2 wherein said oleiin pylene tetramer.

7. The process of claim 2 wherein said promoter is borotungstic acid.

8. The process of of claim 2 wherein said temperature is between about 25 C. and 40 C.

9. The process of claim 2 wherein the BF3 is present in an amount, in excess of 1 mole per mole of hydrate water, such that the free-BF3 to olefin weight ratio is between about 0.2 and 1.5. v 10. An alkylation process which comprises contacting isobutane and ethylene in a molar ratio of isobutane to ethylene between about 2 and 25 at a temperature between about -20 C. and 100 C. at a pressure between about 200 and 1000 p. s. i., said pressure being sufficient to keep a substantial portion of said reactants in the liquid state for a time suiiicient to permit an appreciable amount of alkylation reaction to take place, in the presence of a catalyst pair comprising essentially (a) an acid-B173 complex consisting of borotungstic acid containing water of hydration, and about 1 mole of BFa per mole of hydrate water present in said acid, and (b) boron triuoride in an amount such that the weight ratio of free-EP3 to ethylene charged is at least about 0.2, removing product hydrocarbon mixture containing alkylate product from said contacting zone and separating alkylate hydrocarbon product from unreacted isobutane and ethylene.

11. The process of claim 10 wherein the temperature is between about 25 C. and 40 C.

12. The process of claim 10 wherein said free-BF3/ ethylene weight ratio is between about 0.35 and 1.

is pro References Cited in the iile of this patent UNITED STATES PATENTS 

1. AN ALKYYLATION PROCESS COMPRISING CONTACTING (A) AN ALKYLATABLE FEED HYDROCARBON FROM THE CLASS CONSISTING OF (1) ISOPARAFFIN HAVING FROM 4 TO 8 CARBON ATOMS AND (2) AROMATIC HYDROCARBON AND (B) AN OLEFIN HAVING FROM 2 TO 12 CARBON ATOMS, IN THE PRESENCE OF A CATALYST COMPRISING ESSENTIALLY (I) A PROMOTER CONTAINING WATER OF HYDRATION SELECTED FROM THE CLASS CONSISTING OF BOROTUNGSTIC ACID CADMIUM BOROTUNGSTATE AND NICKEL BOROTUNGSTATE, AND (II) BF3, SAID BF3 BEING PRESENT IN AN AMOUNT IN EXCESS OF ABOUT 1 MOLE PER MOLE OF WATER OF HYDRATION IN SAID PROMOYTER, AT A TEMPERSTURE BETWEEN ABOUT -30*C. AND A TEMPERATURE SUBSTANTIALLY BELOW THE TEMPERATURE AT WHICH SAID PROMOYTER DECOMPOSES, AND AT A PRESSURE SUFFICIENT TO MAINTAIN A SUBSTANTIALLY BELOW OF SAID REACTANTS IN THE LIQUID STATE, AND SEPERATING A HYDROCARBON PRODUCT MIXTURE CONTAINING ALKYLATE PRODUCT OF SAID FEED HYDROCARBON AND SAID OLEFIN. 